1. Field of the Invention
The present invention relates to control systems for raising and lowering window units.
2. Prior Art
In the prior art, various devices comprising means for opening and closing windows in a mechanical manner have been advanced. For example, U.S. Pat. No. 1,816,258 shows a crank operated means for opening and closing windows, but one which operates in a much different manner. The unit uses a pulley arrangement which increases the speed of operation of the cable, and thus decreases the mechanical advantage of the operator. While a pulley arrangement is used in some instances in the present device, the intent is opposite, that is in the present device pulley arrangements are used to increase the mechanical advantage for lifting heavier windows. Likewise, the gear box utilized in the present invention is designed to be low cost, and adaptable to a wide variety of different types of installations.
U.S. Pat. No. 2,547,196 shows a type of a latch for an overhead door that will automatically latch and prevent the door from being opened, and when a particular chain is under tension the door may be raised. A somewhat similar type of lock for a window guard is shown in U.S. Pat. No. 1,592,932.
U.S. Pat. No. 288,282 shows an early form of a self-storing screen for a window that can be raised and lowered, and also a similar device is shown in U.S. Pat. No. 441,088.
My U.S. Pat. No. 3,755,967 shows a hydraulic window operator used for raising and lowering glass units.